Battery Relocation Question

On an MSD, you wire the "large black" and "large red" to hot power. The power on /off occurs on the "small red" wire..........think of it like a relay trigger, that is, very low current.

So what you could do is to eliminate the relay / continuous duty solenoid, and wire the output of the small terminals on the disconnect to the "small red" on the MSD

So you have ignition switch............to small disconnect terminals.........back up front to MSD small red.

That way the disconnect kills power to the ignition and kills the engine.